Home Articles Veterinary medicine Articles Diabetes in cats and dogs
Diabetes in cats and dogs
Diabetes mellitus strikes 1 in 400 cats and a
similar number of dogs. Symptoms in dogs and cats are similar
to those in humans. Generally, most dogs and about half of cats
experience type-1 (insulin-dependent) diabetes, rather than the
type-2 that's now becoming common in obese humans. The condition
is definitely treatable, and need not shorten the animal's life
span or life quality. Untreated, the condition leads to blindness
in dogs, increasingly weak legs in cats, and eventually malnutrition,
ketoacidosis and/or dehydration, and death.
Cats and dogs will generally show a gradual
onset of the disease over a few weeks, and it may escape notice
for a while. The condition is unusual in animals less than 7 years
old. The first obvious symptoms are a sudden weight loss or gain,
accompanied by excessive drinking and urination. Appetite is suddenly
either ravenous (up to 3 times normal) or absent. In dogs, the
next symptom is vision problems and cataracts, while in cats the
back legs will become weak and the gait may become stilted or
wobbly. A quick test at this point can be done using keto-strips
(the same as used on the Atkins diet) or keto/glucose strips,
with your pet. If the keto/glucose strips show glucose in the
urine, diabetes is indicated. If either strip shows ketones in
the urine, the pet should be brought to an emergency clinic right
Watch for noticeable thinning of the skin and
apparent fragility -- these are also serious and indicate that
the pet is consuming all its body fat. Dehydration is also common
by this point, and death can follow quickly.
First, get a diagnosis from your veterinarian
immediately. Diabetes can be treated but is life-threatening if
left alone. Early diagnosis and treatment can help, not only in
preventing nerve damage, but in some cases can even lead to a
Diet is a critical component of treatment, and
is in many cases effective on its own. For example, a recent mini-study
showed that many diabetic cats stopped needing insulin after changing
to a low-carbohydrate diet. The rationale is that a low-carb diet
reduces the amount of insulin needed and keeps the variation in
blood sugar low and easier to predict. Also, fats and proteins
are turned into blood glucose much more slowly and evenly than
carbohydrates, reducing blood-sugar highs right after mealtimes.
Some veterinarians recommend a high-fiber diet
with medium-level carbohydrates instead, but this theory is no
longer credited for cats, though it may be for dogs.
It's now becoming clear that lower carbohydrate
diets will significantly lower insulin requirements for diabetic
cats. Carbohydrate levels are highest in dry cat foods (even the
expensive prescription types) so cats are best off usually with
a low-carb healthy canned diet.
Oral medications like Glipizide that stimulate
the pancreas promoting insulin release, (or in some cases, reduce
glucose production) work in some small proportion of cats (Most
dogs are Type I diabetics so oral hypoglycemic drugs are usually
not prescribed for them), but these drugs may be completely ineffective
if the pancreas is not working. Collective experience from the
Feline Diabetes Message Board indicates that 4-6 weeks is a maximum
trial period for oral medication -- if it's ineffective, the cat
is starving, and longer can harm the cat. Don't be reluctant to
switch from pills to insulin injections -- the difference in cost
and convenience is minor, (many cats are easier to inject than
to pill!) and injections are more effective in most cases.
Humans with Type-1 diabetes are often treated
with a "basal plus bolus" method, where a long-acting
insulin is injected once or twice daily to provide a "basal"
insulin level, then shorter-acting insulin is used just before
mealtimes. For cats and dogs a "basal" method is usually
employed instead -- a single slow-acting dose, twice daily, attempts
to keep the blood sugar within a recommended range for the entire
day. In this case it's important for the pet to avoid large meals
or vigorous exercise sessions, since both can seriously affect
the blood sugar. (Meals may also be timed to coincide with peak
insulin activity.) Once-daily doses are not recommended for pets,
since insulin metabolizes faster in cats and dogs than in humans;
an insulin brand that lasts 24 hours in people may only be good
for about 12 in a cat.
Cats and dogs may be treated with animal insulins
(pork-based seems to work best in dogs, beef-based in cats), or
with human or synthetic insulins. The best choice of insulin brand
and type varies between pets and may require some experimentation.
One of the popular insulins, Humulin N /Novolin N/ NPH, is reasonable
for dogs, but may be a poor choice for cats, since cats' metabolisms
run about twice as fast. Until the early 1990's, the most recommended
type for pets was beef/pork-derived PZI], but that type was phased
out over the 1990's and is now difficult to find in many countries.
There are sources in the US and UK, and many vets are now starting
to recommend them again for pets.
Two new ultra-slow time-release synthetic insulins
are just becoming available in 2004 and 2005 for improving basal
stability, generically known as Insulin Detemir ("Levemir")
and Insulin Glargine ("Lantus"). A mini-study at the
University of Brisbane, Australia has had remarkable results with
Insuline Glargine in cats. No studies have yet been performed
on pets with Detemir/Levemir, but early anecdotal evidence shows
that it is also very effective on cats.
Neuropathy in cats
The weak legs syndrome is a form of neuropathy,
in particular caused by damage to the myelin sheath of the peripheral
nerves caused by poor circulation and cell starvation. Most common
in cats, the back legs become weaker until the cat displays "Plantigrade
stance", standing on its hocks instead of on its toes as
usual. The cat may also have trouble walking and jumping, and
may need to sit down after a few steps. Some recommend a form
of vitamin B12 called methylcobalamin to heal the nerve damage.
Neuropathy often heals on its own within 1 to 3 months once blood
sugar is regulated, but anecdotal evidence points to a higher
success rate with these supplements.
Blindness in dogs
Dogs' eyes are highly sensitive to high blood
sugar, and will have blurred vision, cataracts, or even total
blindness after as little as a few days at blood glucose concentration
above 16.7mmol (300 mg/mL). Cataracts may be treated later, but
blindness is permanent in some cases. Fortunately, dogs rely more
on smell and hearing than on vision, and so may surprise you with
how well they get along without their eyes.
Dosage and Regulation
Cats and dogs may in some cases have their mealtimes
strictly scheduled and planned to match with injection times.
In other cases where the pet free-feeds and normally eats little
bits all day or night, it may be best to remain on this schedule
and try to use a very slow-acting insulin to keep a constant level
of blood glucose. Consult your veterinarian. Note that some veterinarians
still use the outdated recommendation of using Humulin "N"
or NPH insulin for cats. This insulin is too fast-acting for most
cats (though fine for dogs and humans). Cat metabolism runs about
twice as fast as human, so Humulin L or U are better insulins
to begin with.
The goal at first is to "regulate"
the pet's blood glucose, which may take a few weeks or even many
months. This process is basically the same as in type-1 diabetic
humans. The goal is to keep the blood glucose values in a comfortable
range for the pet during the whole day, or most of it.
The recommended method is to Start Low - Go Slow:
- Have an initial blood curve taken over 24 hours at the vet
and receive an initial dosage recommendation.
- The initial dosage will be very conservative (low) (usually
between 0.5 and 2.5 units daily, split into 12-hour dosages)
and may not affect the pet's symptoms noticeably at first.
This is necessary because although high blood sugar can kill
within weeks, low blood sugar can kill in minutes. Dosage
must be increased gradually and carefully. The usual recommended
method is to increase the dose by 1/2 to 1 unit every 7 to
14 days, followed by further glucose testing. Buying an inexpensive
blood glucose meter and testing for yourself is essential
-- it will save many expensive trips to the vet, avoid dangerous
overdoses, and give you a better handle on the pet's ongoing
condition. Urine strips are not accurate enough for this.
- Your pet is "regulated" when its blood glucose
remains within an acceptable range all day, every day. Acceptable
varies somewhat between cats, dogs, and vets, but is roughly
from 5 to 16.7 mmol/L (90 to 300 mg/mL in the USA) for cats,
and between 5 and 14 (90 to 250) for dogs. (The range is wider
for diabetic animals than non-diabetic, since shots cannot
replicate the accuracy of a working pancreas.) It's important,
though, that the glucose level be in the lower half of that
range for as much of the day as possible. If you are not doing
home glucose testing, some vets recommend that you stop increasing
the dosage when the dog or cat is drinking normally, urinating
normally, and eating normally, although organ damage may continue
in some cases until glucose is below the "Renal Threshold"
-- testing urine with keto/glucostix will show when this has
- Obstacles to regulation:
- Sometimes your pet will suddenly appear to need less insulin
than before. If this happens (their blood sugar will go
lower than usual one day), drop the dose immediately and
call your vet. If testing just before an injection, and
the reading is much lower than expected, it may be wisest
to skip that dose and continue retesting every 2-3 hours.
If the drop is dramatic and leads to a hypoglycemic episode
(see below), the cat's sensativit to insulin may increase
dramatically. You should consider dropping their dose after
consulting your veterinarian, and raise it only by half
to one unit per 5-7 days, as before.
- Sometimes your pet's blood sugar will suddenly seem much
higher than usual. This is not a good time to increase their
insulin dosage -- quite the opposite. It often indicates
that a low blood sugar condition (or rapid sugar drop) was
experienced a few hours before, and a Somogyi rebound is
in progress. To be sure, drop the next dose by 15%-50% and
take glucose readings every 4 to 8 hours until the glucose
levels out. Then wait a few more days for the Somogyi hormones
to decrease in the body, and then you can increase again
by 0.5-unit steps every 5-7 days. If you experienced this
rebound, chances are that your original dose was too high,
so you should try to find an ideal dose at a lower point.
- Chronic overdose masked by Somogyi: A dose that is fractionally
too high can easily cause a Somogyi rebound, which can look
like a need for more insulin. This condition can continue
for days or weeks, and it's very hard on the cat's metabolism.
See more on this topic in the Somogyi section below.
- High-carb cat/dog food: Many commercial foods (especially
"Light" foods) are extremely high in cereals and
therefore carbohydrates. The extra carbohydrates will keep
the cat or dog's blood sugar high, and if you're free-feeding
may also make the blood sugar curve over the course of the
day unpredictable. In general, canned foods are lower in
carbohydrates than dry ones, and canned "kitten"
foods lower still. Recent studies show that cats' diabetes
can be better regulated and even sometimes cured with a
low-carbohydrate diet. This may not apply to dogs. If switching
to a lower-carbohydrate food, do it gradually and lower
the insulin dosage appropriately, with your vet's help.
If your cat is on a special diet for pancreatitis, chronic
renal failure, or any other condition, treat that condition
first (don't change diet), it is better to control the blood
glucose with insulin.
- Wrong insulin: Different brands and types of insulin have
idiosyncratic effects on different cats and dogs. If you've
settled on a dose that seems to keep the pet's blood sugar
within range at peak effectiveness, but the sugar readings
remain dangerously high at shot times, the insulin may not
be lasting long enough for your pet, or may not be the best
choice. Switching to a slower-acting or a better-tolerated
insulin for that pet, and lowering the dose initially to
be safe, may be the next step.
Absolute numbers vary between pets, but for general
guidelines only, the levels to watch are approximately:
this is an average non-diabetic pet's
level, but leaves little margin of safety for a diabetic.
a common minimum safe value for the
lowest blood sugar of the day
desired range for diabetics (non-diabetic
range is 40-130 but usually unsafe to aim for)
"Renal Threshold" excess glucose
from the kidneys spills into the urine, pet begins to
show diabetic symptoms. Long term damage to eyes, nerves,
and other organs if glucose remains above here too often.
the maximum safe value for the highest
blood sugar of the day, in dogs, to avoid short-term eye
the maximum safe value for the highest
blood sugar of the day, in cats, to avoid short-term nerve
The regulation process is described in more detail
Detecting and avoiding Chronic Somogyi Rebound
It's confusing but true: Too little insulin
means pre-shots are too high; too much insulin often also means
pre-shots are too high. This effect is often noted by those who
test their pets' blood glucose at home.
The reason: Anytime the glucose level drops too
far or too fast, the cat or dog will defensively dump glycogen
from the liver, as well as hormones epinephrine and cortisol,
into the bloodstream. (If these are insufficient, hypoglycemia
ensues!) The glycogen raises the blood glucose, the other two
make the pet insulin-resistant for a day or two. This phenomenon
was first documented by a Dr. Somogyi..
Alternating high and low blood sugar numbers with no apparent
logic usually mean repeated Somogyi Rebound. High, flat, unresponsive
blood sugar over a period of days is also a typical Chronic Somogyi
Rebound sign. This pattern occurs mostly with long-duration insulins
given in overdose amounts. Sometimes this high flat curve will
be punctuated by sudden drops to very low values, (with possible
hypoglycemic events) followed by more high unresponsive numbers.
Even when raising the insulin dose slowly and
carefully, it's possible to pass the correct dose and go on to
a slight overdose. (A typical case is increasing bidaily dosage
from 1 unit to 2, passing a correct dose of 1.5 units.) This may
produce a rebound -- a swift jump in blood glucose up from a dangerously
low reading, to beyond the previous pre-shot level. The pet may
be a bit less responsive to the same dose the next shot, from
those other hormones.
According to recent experience on internet diabetes
forums, this phenomenon may be less dramatic and more common than
usually thought. The term "mini-rebound" is beginning
to gain currency. If your insulin dose is just a smidgen high,
you may see either nothing at all, or a hypoglycemic episode or
a mini-rebound. Some Feline Diabetes Message Board regulars describe
A normal rise will instead be slow and gradual.
One way to tell the difference is to take a "curve"
(repeated tests every 2 hours) on a weekend and look for the shape
of the curve. If the curve is valley-shaped, and gradual, with
lowest point in normal glucose ranges (60-130), all is well. Other
shapes should arouse suspicion. To check if this is a rebound,
the only sure way is to reduce dosage and look for a flatter curve.
Anytime blood glucose numbers seem higher after
dosage is raised, consider the possibility of a somogyi rebound.
An acute hypoglycemic episode (very low blood
sugar) can happen even if you are careful, since pets' insulin
requirements sometimes change without warning. The symptoms are
depression/lethargy, confusion/dizziness, loss of excretory/bladder
control, vomiting, and then loss of consciousness and/or seizures.
As soon as possible, administer honey or corn syrup by rubbing
it on the gums (even if unconscious, but not if in seizures),
and rush it to the vet. Carry more honey or corn syrup with you
on the way and keep rubbing it on the gums, where it can be absorbed
-- it could save the pet's life. Every minute without blood sugar
causes brain damage. (Some recommend administering syrup anally
if the animal is in seizures!)
If the pet has hypoglycemia according to the
blood glucose meter, but no symptoms, give treats or food if possible.
If they won't eat, administer some honey followed by food or cat
treats, and continue to do so until the blood glucose is rising,
and the latest insulin shot's peak action is past.
Sometimes a mild hypoglycemic episode will go
unnoticed, or leave evidence such as an "accident" where
kitty fails to make it to the litterbox. In these cases the blood
sugar will probably appear paradoxically high upon the next test
hours later, since the pet's body will react to the low blood
sugar by stimulating the liver to release stored glycogen. This
condition is known as Somogyi rebound (see link above), and requires
a lowered insulin dosage for the next few days. The Somogyi rebound
may also occur when the pet's blood glucose drops too rapidly,
even if it never actually reaches a low reading.
Remission in cats
It is in many cases possible to induce remission
(a temporary or permanent freedom from insulin-dependence) in
cats. (This appears to be peculiar to cats.) There is little agreement
among experts on how this is reliably achieved, but it does happen
in 20, 30, or even 40 percent of cats who are properly regulated
quickly. Chances of success are highest in the first few months
after initial diagnosis. A likely explanation is that a damaged
cat's pancreas can sometimes regenerate itself, but continued
high blood-sugar is toxic to the pancreas and prevents regeneration.
A combination of low-carb healthy diet, well-chosen insulin, and
well-chosen dosage plans can in many cases heal a damaged pancreas
and allow the cat's blood sugar to be controlled entirely by diet